The present invention relates to a steering control system of a motor vehicle and, more particularly, to a rear wheel steering control system of the motor vehicle in response to signals representing vehicle speed.
In a known art, there is provided a control system for steering rear wheels of the motor vehicle in which the rear wheels are automatically steered in response to steering angles of front wheels. The control system of this type is disclosed in the Japanese Patent Laid-open Publication No. 61-175183, in which the control system includes first and second vehicle speed sensors located at two portions of the vehicle, means for determining whether a difference value between output signals from the first and second speed sensors is above or below a predetermined value, and means for restricting the rear wheels from over-steering more than a predetermined value such that the difference value between the output signals from both the speed sensors is above the predetermined value.
However, in the steering control system of the type described above, when the difference value between the output signals from the two speed sensors is above the predetermined value, the steering of the rear wheels is prohibited on the discrimination of abnormal condition of the speed sensors located at two portions of the vehicle body. Accordingly, in a case where the predetermined value is preliminarily set to a desired value in a low speed operation area of a vehicle, the control system will liably detect the difference value, as an abnormal value, which may not be an abnormal difference value in a high speed driving of the vehicle.